Summary Stuttering or childhood onset fluency disorder, affects 5-8% of preschool-aged children. Although many children?s stuttering resolves within 12-24 months of onset, those who continue to stutter beyond age 7 are at significant risk for chronic stuttering. For children who persist, speaking often becomes a lifelong struggle. The negative consequences for academic/vocational achievement and psychosocial development suffered by many of these children are substantial and long lasting. Prior studies in preschool children who stutter (CWS) have identified demographic, behavioral, and physiological factors associated with stuttering persistence by comparing performance across groups of preschool children. Yet, we do not know how a child?s unique developmental pathway leads them to recover or persist in stuttering. This limits our ability to predict a child?s risk of developing persistent (chronic) stuttering reliably and to develop efficacious prevention and treatment strategies. This project shifts experimental focus, for the first time, to the individual child, providing a dynamic account of how neurological, behavioral, and experiential factors unfold over time and contribute to different stuttering outcomes. We achieve this through our comprehensive, longitudinal design and structural equation modeling framework, in which we map the developmental trajectories of critical factors implicated in stuttering. In our approach, we use a novel neuroimaging technique, functional near-infrared spectroscopy (fNIRS), that allows us to record brain activity concurrent with continuous speech production, a distinct advantage of this technique. We will assess whether neural markers derived from fNIRS recordings identified in our research with older CWS can distinguish preschool children at risk for persistence, thereby helping to establish a neural basis for stuttering persistence and recovery. We will also assess whether atypical coupling between sympathetic nervous system activity and speech output, detected in cross-sectional studies, represents a risk factor for chronic stuttering. Finally, stuttering leaves a lasting imprint on children who persist. Ample evidence shows that older children and adults are more likely to harbor negative emotions about their speech and/or develop communication anxiety. We lack a continuous picture, however, of how these issues develop in young children whose awareness of stuttering is emerging. We will examine how behavioral, emotional, and experiential factors unfold over time and explore their roles in stuttering persistence or recovery and in the development of negative communication attitudes. This project will bring new, comprehensive insights into why stuttering persists in individual children, and, in parallel, help better prioritize therapy resources, identify etiological targets for prevention and intervention, and accelerate the development of new treatments.